1. Field of the Invention
The present invention relates to a method of fabricating on-chip spacers for a TFT (thin transistor film) panel, and more specifically to a simple and cheap method for easily and accurately fabricating on-chip spacers on an opaque region of a TFT panel.
2. Description of Related Art
A simple method of fabricating a TFT display device includes steps of.
(1) preparing a first glass;
(2) forming a driving circuit and pixel electrodes on the first glass;
(3) applying an orientation film on the pixel electrodes to from a TFT plane;
(4) defining a frame region;
(5) forming spacers in the frame region;
(6) attaching a second panel to the first glass;
(7) filling the frame region with liquid crystal; and
(8) pressing the first and second panels together to securely combine them.
Beside the basic steps of the method we mentioned above, this method can further add other steps depending on display requirements, such as display function, driving circuit, etc.
FIG. 10 illustrates a TFT panel with a matrix active driving circuit composed of transistors (52), data lines (53), scan lines (54) and pixel electrodes (55). The transistors (52), data lines (53) and scan lines (54) are opaque and form an opaque regions (501) that separate multiple window regions (500).
Further, the spacers (60) for providing holding liquid crystal space between the first and second glasses are formed on the TFT driving circuit. There are two common methods used to fabricate the spacer on the TFT panel. One of which is a spraying technique as a first method, and the other of which is an on-chip spacer technique as a second method.
In the first method, the spacers (60) are sprayed on the TFT panel (50) so the first method is easy. However, the number and location of spacers (60) on the TFT panel (50) cannot be accurately controlled during spraying the spacers (60). Therefore, the spacers (60) may be deposited on windows (500) of the TFT panel (50) and cause a light leakage fault to affect display quality.
In the second method, the spacer can be formed only on the opaque region of the TFT panel. The second method has steps of
(a) coating the TFT panel with photoresist;
(b) transferring a spacer pattern corresponding to the opaque region (501) on the photoresist by a stepper or scanner exposure machine;
(c) removing exposed photoresist to form the spacer pattern on the TFT panel; and
(d) curing the photoresist to form the spacer.
The second method can accurately form the spacers on the opaque region of the TFT panel by exposing the photoresist technique. However, the spacers on a high resolution TFT display device is formed by an expensive, high-precision exposure machine. Therefore, the second method of fabricating spacers has higher cost than the first method.
The present invention provides a simple, cheap and accuracy method of fabricating on-chip spacers on high dpi TFT display devices to mitigate or obviate the aforementioned problems.